If you look at the picture of the KMC Missing Link above, the plates are identical but not symmetric. Therefore, the orientation does matter. The shape of the side with the pin is rounder while the side with the slot is more oval shaped. When downshifting, do you want the rounder side to contact the upper part of the cogs first or the oval side? It's a bit hard to describe, but does my question make sense?

It's been my experience with KMC Missing Links for several years now, for thousands of miles on more than a handful of bikes, that the orientation doesn't matter on either the 9-speed or 10 speed links. I pay no attention to the orientation of the link when I install it, I just install it. I've had them on a variety of chains, including the new 6700 chain and they've always worked dandy.

By the way, you'll need the missing link at the upper run of the chain, if you need to actually apply pressure to the chain to get it to seat properly.

I always install the master link on the lower run of the chain since it's a lot easier to get slack there using a "hairpin" tool to hold the loose ends of the chain in proximity. After the link is in place and pulled snug, I carefully crank it around to the top run and give the pedal a wack with my hand to assure the link is fully seated.

I always install the master link on the lower run of the chain since it's a lot easier to get slack there using a "hairpin" tool to hold the loose ends of the chain in proximity. After the link is in place and pulled snug, I carefully crank it around to the top run and give the pedal a wack with my hand to assure the link is fully seated.

Precisely what I do. Except my hands are fragile, so I hold the rear wheel/tyre and push forward on the pedal instead.

Originally Posted by Laplacian

If you look at the picture of the KMC Missing Link above, the plates are identical but not symmetric. Therefore, the orientation does matter. The shape of the side with the pin is rounder while the side with the slot is more oval shaped. When downshifting, do you want the rounder side to contact the upper part of the cogs first or the oval side? It's a bit hard to describe, but does my question make sense?

1 link out of an average of ~ 110-116 is going to affect shifting in any appreciable manner.

1 link out of an average of ~ 110-116 is going to affect shifting in any appreciable manner.

Okay maybe the orientation won't affect shifting. How about safety? Is one orientation safer?

I know a couple of you have said "no" but Shimano goes to a lot of trouble to tell us where to install the pin on their standard pin chains. This is an entirely differently shaped link--shouldn't installation be even more important? I don't really understand why Shimano says a certain way is a lot stronger for their fixed pin installation so I can't seem to apply that same logic here.

Okay maybe the orientation won't affect shifting. How about safety? Is one orientation safer?

I know a couple of you have said "no" but Shimano goes to a lot of trouble to tell us where to install the pin on their standard pin chains. This is an entirely differently shaped link--shouldn't installation be even more important? I don't really understand why Shimano says a certain way is a lot stronger for their fixed pin installation so I can't seem to apply that same logic here.

Whichever way you install it, it's the opposite on the other side. There can be no advantage strength wise, at least along the length of the chain. Again, if it was a safety issue, KMC would've stated this explicitly in their installation documents. They don't want to be sued anymore than you do.

Regarding the joining pins, Campy insists that the end of the pin with the shoulder should be on the left side of the chain, so the pin installation is done from the left side.

When installing a second replacement pin in a Shimano chain, they say to push the new pin in the same direction as the old one was pushed out. That would most often place the shoulder on the right side, since most people work on the right side of a bike. They also show the original joining pin being pushed in from the right side.

As for the master link, I place the slotted end pointing toward the back of the bike, on the lower section of chain, as viewed from the right side - just the opposite of the the link in the picture. I do that only because it's required for a Wipperman connex link to work properly and has become a habit.

I'd like a rationale to why (official or not) they state this. I can only think of one reason.

I'd say it has to do with potential burrs generated from pushing the old pin out. Better not to upset a burr by shoving a pin back from the opposite side.

The other reason might be potential damage to the hole in the outer plate. The right side might see damage, but not the left, since the peened end of the pin is pushed through the right side. The new pins have a little shoulder on the end that would be against the potntially damaged hole.

Both scenerios make sense.

Most chains I've used actually shear off a ring of peened material from the pin when it's pushed through. The drive pin on my chain tool has a collection of little steel rings on it.

Thanks to all for the replies. One last question: is it safe to reuse the KMC Missing Link over and over? I find that removing the chain makes it easier to clean and lube. I would, of course, replace the KMC Missing Link when I replace the chain. But does it need to be replaced more often? I know some SRAM Power Links were 1-time use (although others re-use them also). Thanks.

(Not trying to start a debate on whether this is good practice or not, which lube to use, if you should ever clean a chain, etc.)

Thanks to all for the replies. One last question: is it safe to reuse the KMC Missing Link over and over? I find that removing the chain makes it easier to clean and lube. I would, of course, replace the KMC Missing Link when I replace the chain. But does it need to be replaced more often? I know some SRAM Power Links were 1-time use (although others re-use them also). Thanks.

(Not trying to start a debate on whether this is good practice or not, which lube to use, if you should ever clean a chain, etc.)